Bug 1340076 - Force tiling to always be enabled on OSX. r=nical

gfx/layers/client/ClientPaintedLayer.cpp

@@ -149,7 +149,13 @@ already_AddRefed<PaintedLayer>
 ClientLayerManager::CreatePaintedLayerWithHint(PaintedLayerCreationHint aHint)
 {
   NS_ASSERTION(InConstruction(), "Only allowed in construction phase");
+  // The non-tiling ContentClient requires CrossProcessSemaphore which
+  // isn't implemented for OSX.
+#ifdef XP_MACOSX
+  if (true) {
+#else
   if (gfxPrefs::LayersTilesEnabled()) {
+#endif
     RefPtr<ClientTiledPaintedLayer> layer = new ClientTiledPaintedLayer(this, aHint);
     CREATE_SHADOW(Painted);
     return layer.forget();